Unassigned Area Codes

Area codes are an important component of the telephone numbering system that allows routing calls to the right locations. In the United States, there exists an organization called the North American Numbering Plan Administrator that is responsible for the administration and management of telephone area code numbers and planning.

Part of the responsibilities of this Administrator includes reserving certain area codes that remain unassigned. These unassigned area codes are basically area code numbers that cannot be currently used for call routing, but are kept aside for potential future requirements.

When new geographical areas need to be allocated phone numbers for use by telephone subscribers, or when a current area code nears full capacity utilization, the Administrator can pull from this reserve of unassigned area codes. This ensures that there continues to remain an available pool of number blocks that can be assigned to fulfill future needs.

Unassigned area codes may also be set aside specially for designating nationwide utility services like 811, used as an easy single dial access to One Call systems that help track underground pipeline infrastructure prior to any digging work being undertaken. This prevents unsafe damage to pipelines. In this manner, keeping some area codes unassigned caters to specific federal level services on an as-needed basis, beyond just geographic consumer phone number allocation.

At the same time, callers who wish to spoof phone numbers to scam and spam individuals will often use combinations of random digits for invalid area codes followed by made up phone line numbers. When you receive an incoming call tagged with an area code designated as unassigned in records, it signals an illegitimate caller ID that cannot originate from a valid subscribed number.

Being cognizant that numerous area codes are reserved from allocation allows quicker identification of such scam calls pretending to use phone numbers tied to nowhere. Examples include area codes like 473, 539, 551 that are unassigned number blocks set aside for the future.